1. Technical Field to which the Invention Belongs
The present invention relates to an edge blending device for suppressing an increase in a luminance of an overlap area in which projection lights overlap each other, a light shielding device which shields the projection lights, and a multi-projection system which includes a plurality of projection units.
2. Description of the Related Art
In a multi-projection system in which is arranged a plurality of projectors serving as projection units, in a case in which an overlap area in which projection lights from adjacent projectors overlap each other is formed, in order to prevent a luminance of the overlap area from increasing compared with other areas, for example, it is necessary to apply some edge blending process, such as a level adjustment of an image signal corresponding to the overlap area of the projection lights projected by the individual projectors, a use of optical shielding unit, or a combination of both. By applying the edge blending process, it is possible to realize a high quality, large screen image in which no seam is noticed between adjacent projection lights.
An edge blending technology which adjusts an image signal level of the overlap area (referred to as a signal processing type edge blending technology) can be realized by using a dedicated image processing device manufactured for that purpose. However, this kind of dedicated image processing device is very expensive on account of being special-purpose dedicated hardware.
Also, although the signal processing type edge blending technology is rich in flexibility such as an easy setting in units of one pixel and an easy changing of a gradation level, there is also a problem in that a so-called “black floating” cannot be solved only by adjusting the image signal level.
Meanwhile, in an edge blending technology using the optical light shielding unit including a light shielding plate and a dark filter (referred to as an optical type edge blending technology), there is basically no need to process and treat the image signal itself and, as well as it being possible to suppress the “black floating”, there is an advantage of being inexpensive.
FIGS. 15A and 15B schematically illustrate an example in which light shielding plates are used as the optical type edge blending technology. As shown in FIG. 15A, light shielding plates 20 corresponding to side edges of projection lights G1 and G2 from two projectors PJ11 and PJ12 are installed in respective defocusing areas and, as shown in FIG. 15B, a projection is carried out in such a way as to form an overlap area in the side edges of the individual projection lights.
FIGS. 16A and 16B show respectively a luminance level in the overlap area in a case of providing no light shielding plate, and a luminance level in the overlap area in a case of providing the light shielding plates. As can be seen from FIGS. 16A and 16B too, in the case of providing no light shielding plate 20, the luminance level increases in the overlap area (FIG. 16A) while, in the case of providing the light shielding plates 20, it is possible to suppress an increase in the luminance level in the overlap area (FIG. 16B). At this time, a black floating due to a leaked light caused by an optical modulator being unable to shield light can also be suppressed, as the leaked light can be shielded.
In this way, the optical type edge blending technology, as well as being able to solve the problem of the “black floating”, has a feature of being inexpensive. Meanwhile, however, there is also a need to move light shielding unit such as the light shielding plates for the purpose of changing a form of usage as the multi-projection system or adjusting (whether manually or automatically) projection lights from projectors configuring the multi-projection system. As the movement of the light shielding unit, for example, a movement of the projection lights in an inward direction or an outward direction, a position adjustment within the projection lights, and the like can be considered.
As used herein, the “changing of the form of usage as the multi-projection system” refers to a changing of a combination of projectors, among the plurality of projectors configuring the multi-projection system, which carry out a projection, it being supposed that a display mode on a screen is switched. A specific example of the switching of the display mode will be described hereafter.
When this kind of display mode switching is carried out, as a pattern of an overlap area occurring between the projection lights from the individual projectors which carry out the projector also changes in many cases, a light shielding pattern corresponding to the pattern of the overlap area at that time is formed. For this reason, it is necessary to carry out an adjustment of the light shielding unit, such as a movement of the light shielding unit, for each projector.
At this time, in the event that there is a small number of projectors configuring the multi-projection system, it is not so difficult to manually carry out the adjustment of the light shielding unit but, in the event that there is a large number of projectors, or the projectors are installed in a high position or the like which is difficult to reach, a manual adjustment of all the light shielding unit is a very time-consuming operation, and there is also a problem in that it is impossible to quickly switch the display mode.
In order to respond to these kinds of problem, a technology enabling the light shielding unit to be automatically adjusted has also been proposed (for example, JP-A-2001-268476). In the technology disclosed in JP-A-2001-268476, one certain projector is provided with position control unit capable of an independent position control of four light shielding plates corresponding to four side edges of projection lights from the projector, enabling the position control of the four light shielding plates in a left and right direction or an up and down direction.
According to the JP-A-2001-268476, it is possible to obtain an advantage that a position control of each light shielding plate for changing a light shielding pattern along with the change in the pattern of the overlap area becomes possible, and that it is also possible to fine adjust the position control, and it is considered possible, by using a luminance sensor, to automatically adjust an area to be light shielded.
Also, in a case in which the plurality of projectors is used as the heretofore described “multi-projection system”, a light source of a projector, among the plurality of projectors, which carries out no projection is normally stopped from emitting light, that is, turned off, causing the projection not to be carried out.
In the technology disclosed in JP-A-2001-268476, the position control unit for carrying out the position control of the light shielding plates for responding to the changing of the light shielding pattern or the like need to be provided, one corresponding to each light shielding plate. As the light shielding plate position control unit, a translation mechanism and its drive unit for enabling the individual light shielding plates to move in the left and right direction or the up and down direction are necessary and, as it also enables the individual light shielding plates to be moved in a range of a prescribed angle, a rotation mechanism and its drive unit for rotating the individual light shielding plates become necessary.
Consequently, in the case in which there is a large number of projectors configuring the multi-projection system, as a large number of light shielding plates is also required as a matter of course, as a light shielding pattern switching mechanism for changing the light shielding pattern, the translation mechanism for moving the large number of light shielding plates in the left and right or up and down direction, the rotation mechanism for rotating the large number of light shielding plates, and their drive unit become necessary, meaning that there is a problem in that, as well as a whole mechanism for carrying out an edge blending becoming very complicated, its control also becomes very complicated.
Also, when using the projectors as the multi-projection system, the projector which carries out no projection is caused not to carry out the projection by the light source being turned off. Consequently, in the projectors configuring the multi-projection system, each time the projection is carried out or not carried out depending on the display mode, the turning off and turning on of the light source are carried out. Incidentally, as an electrode of a lamp (for example, a high pressure mercury-vapor lamp) used for the light source of the projector wears out due to a discharge or the like at the time of the turning on, in some cases, a life of the lamp depends on a number of times it is turned on. Consequently, in a case in which the display mode changes frequently, as the number of times the lamp of the projector is turned on increases, there is a problem in that the lamp life is shortened. Also, a luminance of the lamp is low when it is turned on, and at least requires a time to reach a luminance which is normally used. Consequently, in a case in which the display mode is switched within a short time, there is a problem in that, as well as a brightness not being secured, a luminance difference becomes large in comparison with a projector which is continuously on.